Fix a problem where if a uint64_t value is placed into a python dictionary and...

Fix a problem where if a uint64_t value is placed into a python dictionary and sent up to LLDB and converted to StructuredData, it would not be able to parse the full 64 bit value. A number like 0xf000000000000000L could be placed into a dictionary, and sent to LLDB and it would end up being 0xffffffffffffffff since it would overflow a int64_t. We leave the old code there, but if it overflows, we treat the number like a uint64_t and get it to decode correctly. Added a gtest to cover this so we don't regress. I verified the gtest failed prior to the fix, and it succeeds after it.

<rdar://problem/27409265>

llvm-svn: 278304